1. Field of the Invention
This invention relates to a process for preparing a photosensitive lithographic printing plate precursor (also known as a presensitized plate or a PS plate in short). More particularly, the invention relates to an improved process for preparing a photosensitive lithographic printing plate precursor wherein a silver halide emulsion layer is directly applied to a layer containing a lipophilic resin and dried.
2. Description of the Prior Art
U.S. Pat. No. 3,511,661, Japanese Patent Application (OPI) No. 37804/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") as well as German Patent Application (OLS) Nos. 2,517,711 and 2,640,763 teach a photosensitive lithographic printing plate precursor wherein an ultra-violet sensitive layer conventionally used as a photosensitive layer for PS plates and containing a diazo compound or photopolymer and a silver halide emulsion layer are disposed, in sequence, on a support, such as an aluminum plate, having a hydrophilic surface. But the ultraviolet sensitive layer is water-repellent rather than hydrophobic and does not provide satisfactorily strong bond with a silver halide emulsion layer directly disposed on it. Therefore, during the photomechanical processing of such precursor to make a photosensitive lithographic printing plate (for example, during the development of a silver halide emulsion layer), the emulsion layer can separate from the ultraviolet sensitive layer, and a commercially acceptable product may not be obtained. To eliminate these defects, the provision of an interlayer between the UV sensitive layer and silver halide emulsion layer has been proposed in, for example, U.S. Pat. No. 3,245,793 and U.S. Defensive Patent Publication No. T. 870,022. However, even such interlayers may not provide adequate bond between the UV sensitive layer and emulsion layer, or they may provide so strong a bond that the subsequent removal of the emulsion layer throughout, or in the non-image areas, become difficult. As a result, the lithographic printing plate obtained easily forms stain in the non-image area and provides an image area low in lipid-sensitivity (i.e., the property to receive oily ink). What is more, the provision of such an interlayer adds to production costs, because it requires separate coating and drying steps.